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Search: Phosphorylation[Title] AND translation[Title] AND factors[Title] AND response[Title] AND anoxia[Title] AND turtles[Title] AND Trachemys[Title] AND scripta[Title] AND elegans[Title] AND Role[Title] AND AMP-activated[Title] AND protein[Title] AND kinase[Title] AND target[Title] AND rapamycin[Title] AND signalling[Title] AND pathways[Title]

Phosphorylation of translationfactors in response to anoxia in turtles, Trachemysscriptaelegans: role of the AMP-activatedproteinkinase and target of rapamycinsignallingpathways.

Abstract

Long-term survival of oxygen deprivation by animals with well-developed anoxia tolerance depends on multiple biochemical adaptations including strong metabolic rate depression. We investigated whether the AMP-activatedproteinkinase (AMPK) could play a regulatory role in the suppression of protein synthesis that occurs when turtles experience anoxic conditions. AMPK activity and the phosphorylation state of ribosomal translationfactors were measured in liver, heart, red muscle and white muscle of red-eared slider turtles (Trachemysscriptaelegans) subjected to 20 h of anoxic submergence. AMPK activity increased twofold in white muscle of anoxic turtles compared with aerobic controls but remained unchanged in liver and red muscle, whereas in heart AMPK activity decreased by 40%. Immunoblotting with phospho-specific antibodies revealed that eukaryotic elongation factor-2 phosphorylation at the inactivating Thr56 site increased six- and eightfold in red and white muscles from anoxic animals, respectively, but was unchanged in liver and heart. The phosphorylation state of the activating Thr389 site of p70 ribosomal protein S6 kinase was reduced under anoxia in red muscle and heart but was unaffected in liver and white muscle. Exposure to anoxia decreased 40S ribosomal protein S6 phosphorylation in heart and promoted eukaryotic initiation factor 4E-binding protein-1 (4E-BP1) dephosphorylation in red muscle, but surprisingly increased 4E-BP1 phosphorylation in white muscle. The changes in phosphorylation state of translationfactors suggest that organ-specific patterns of signalling and response are involved in achieving the anoxia-induced suppression of protein synthesis in turtles.